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Sodium channel

sodium channel

(Science: neurology, physiology) The protein responsible for electrical excitability of neurons. A transmembrane ion channel, containing an aqueous pore around 0.4nm diameter, with a negatively charged region internally (the selectivity filter) to block passage of anions.

The channel is voltage gated: it opens in response to a small depolarisation of the cell (usually caused by an approaching action potential), by a multistep process.

Around 1000 sodium ions pass in the next millisecond, before the channel spontaneously closes (an event with single step kinetics). The channel is then refractory to further depolarisations until returned to near the resting potential.

There are around 100 channels per square micron in unmyelinated axons, in myelinated axons, they are concentrated at the nodes of Ranvier. The sodium channel is the target of many of the deadliest neurotoxins.

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Depolarization = ion channel opening?

... statement: "Action potentials are formed when a stimulus causes the cell membrane to depolarize past the threshold of excitation, causing all sodium ion channels to open." Isn't the cell membrane depolarized BECAUSE the ion channels open?

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by autumnsphere
Wed Oct 29, 2014 2:18 pm
Forum: Cell Biology
Topic: Depolarization = ion channel opening?
Replies: 1
Views: 664

Too many ions inside a neuron cell. What happens?

For example, there are diseases where the sodium channel cannot gauge voltage difference effectively, and so it remains open, rapidly building up a concentration ...

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by Coelacanth
Tue Dec 03, 2013 1:34 am
Forum: General Discussion
Topic: Too many ions inside a neuron cell. What happens?
Replies: 1
Views: 2402

Membrane proteins

poroto: I think you're looking rather for something like sodium channel, which has a plug closing the channel after prolonged functioning. Thus, it does actually ...

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by JackBean
Mon Mar 28, 2011 7:34 am
Forum: Cell Biology
Topic: Membrane proteins
Replies: 4
Views: 3035

Sodium Potassium pump

I understand that this involves the movement from low concentration to high concentration, but does it require specalised channel proteins, and why is the phosphate required to change the shape to push the potassium out.

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by Deat
Wed Nov 17, 2010 12:04 pm
Forum: Cell Biology
Topic: Sodium Potassium pump
Replies: 2
Views: 3743

Potassium Channels - Determining the functional amino acids!

... It was assigned to us when we were discussing the selective potassium channels in cells which didn't allow the passage of sodium ions through them. We had to determine the amino acids that are actually functional ...

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by dharavsolanki
Tue Oct 05, 2010 4:44 am
Forum: Cell Biology
Topic: Potassium Channels - Determining the functional amino acids!
Replies: 5
Views: 3783
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